The present invention relates to marine accessories, and more particularly to accessories for marine thru-hull fittings.
Many boats, ships and other marine vessels are provided with thru-hull fittings that allow water or other liquids to vent from inside of the hull to the environment. For example, thru-hull fittings are used to discharge water or other liquids through the hull from a variety of appliances, including air conditioners, bilge pumps, live wells and other apparatus. Thru-hull fittings are also used to drain water from various collection points throughout the boat, such as the cockpit deck, engine cover gutter and anchor locker as well as to vent condensation from holding tanks and the like. Thru-hull fittings are available in a wide variety of designs. FIG. 1 is a sectional view of a conventional thru-hull fitting 100 adapted to vent water received from a discharge hose 130. The discharge hose 130 may serve as a discharge line for an appliance or as a drainage line for a water collection point. Thru-hull fitting 100 includes a flange 104 that engages the outer surface 122 of the hull 120 and a throat 102 that extends from the flange 104 into the interior of the hull. The outer surface of the throat 102 is threaded and receives lock nut 110. The lock nut 110 is tightened against the hull to secure the fitting. FIG. 2 is a sectional view of second type of thru-hull fitting 100' adapted to form a passageway through the hull 120, but not to receive a discharge hose. This type of fitting is often used as a drainage for water collection points located immediately adjacent to the hull. As shown, the throat 102' of this fitting 100' is much shorter in length and the lock nut 110 is replaced by an internally threaded flange 111.
A well-known problem associated with the use of thru-hull fittings is the formation of stains on the outer surface of the hull caused by minerals and other solids contained in the discharged liquid. Thru-hull fittings are typically used to discharge liquids, such as river water, lake water, brackish water and salt water, that contain at least some degree of suspended minerals and other solids. As relatively slow moving liquid is discharged from the fitting, it runs down the outer surface of the hull to the water line. The minerals and other solids contained in the liquid adhere to the surface of the hull leaving stains in a relatively short period of time. Experience has revealed that these stains are often difficult to remove, and a variety of chemical products (e.g. cleaning detergents) and mechanical products (e.g. cleaning brushes and scouring pads) are available on the market to help remove the stains.
U.S. Pat. No. 5,722,339 to Gross is directed to a thru-hull fitting that is modified in an effort to reduce the amount of discharge liquid running along the outer surface of the hull. The Gross patent discloses a thru-hull fitting with an outer flange that is design to separate the discharge liquid from the hull. The Gross flange includes a planar and substantially vertical outer surface and an inclined inner surface. The discharge liquid flows down the outer surface to the bottom edge of the fitting. The inclined inner surface is intended to inhibit the flow of liquid from the outer surface, along the bottom edge and back toward the hull. The Gross thru-hull fitting suffers in several respects. First, in retrofitting applications, the Gross thru-hull fitting requires replacement of the entire thru-hull fitting. Manufacture of an entirely new thru-hull fitting is relatively expensive and creates problems associated with the disposal or recycling of the replaced fittings.
Second, because drip control fittings are not desired in many applications, two entire lines of thru-hull fittings must be manufactured and stocked--one line with drip control flanges and one without. Because thru-hull fittings are available in such a wide variety of styles, shapes and sizes, this is a significant undertaking. Obviously, this increases the overall cost of manufacturing and stocking thru-hull fittings.
Third, as a result of adhesion, the Gross thru-hull fitting may still permit discharge water to flow along the outer surface of the hull. Because of the adhesive and cohesive characteristics of water, discharge liquids have a tendency to adhere or cling to the surface of the thru-hull fitting. Adhesion is a well-known phenomenon that, in effect, creates a force on the liquid directed toward the surface along which it is flowing. In this case, the adhesive force resists separation of the discharge liquid from the fitting--even at the fitting's bottom edge. As sufficiently slow moving liquid reaches the bottom edge of the fitting, adhesion causes the liquid to cling to and roll under the bottom edge of the fitting. The adhesive force is eventually overcome by gravity, but, in the case of sufficiently slow moving liquid, not before it has redirected the flow of liquid inwardly toward the hull. As a result, sufficiently slow moving water may still flow along and stain the outer surface of the hull.